In a typical thermal printer, a web-type carrier containing a repeating series of spaced frames of different colored heat transferable dyes is spooled on a carrier supply spool. The carrier is paid out from the supply spool and rewound on a take-up spool. It moves through a nip formed between a thermal print head and a dye-absorbing receiver. The receiver is in turn supported by a platen in the form of a drum. The print head engages the carrier and presses it against the receiver. The receiver may for example be an I.D. card and the print head is formed of, for example, a plurality of heating elements. When a particular heating element is energized, it is heated. In the presence of heat and pressure, dye from the carrier is caused to transfer to the receiver. The density or darkness of the printed color dye is a function of the energy delivered from the heating element to the carrier. These types of thermal printers offer the advantage of "true continuous tone" dye density transfer. This result is obtained by varying the energy applied to each heating element, yielding a variable dye density image pixel on the receiver.
The web-type carrier often includes a repeating series of spaced yellow, magenta and cyan dye frames. The carrier is typically formed of a very thin, flexible dye carrying member having a thickness that can be in the order of 1/4 mil. First, the yellow frame in the carrier is moved to a position under the print head and as it is advanced. The heating elements are selectively energized to form a row of yellow image pixels in the receiver as the receiver is moved by the drum under the print head. This printer process is repeated until, line-by-line, the entire yellow dye image is formed in the receiver. Next, the magenta carrier frame is moved under the print head and the receiver is advanced to align the starting point of the yellow dye image with the print head heating elements also moved under the print head. Both the receiver and the magenta carrier frame are simultaneously moved through the nip as the heating elements are selectively energized and a magenta image is formed superimposed upon the yellow image. Finally, as the cyan dye carrier frame and the receiver dye image starting point are moved under the print head, the heating elements are selectively energized and a cyan dye image is formed in the receiver superimposed upon the yellow and magenta dye images. The yellow, magenta and cyan dye images combine to form a color image.
The term "card" as used herein, generally refers to flat flexible cards that are formed of a material that has a memory or stiffness--memory or stiffness in this disclosure refers to the ability of a flexible card when curved or bowed to return to a flat condition. Such material can be, for example, polycarbonate, polyester, or resin coated paper. Examples of cards are playing cards, ID cards, business cards, credit cards, drivers' licenses and photographic paper.
It is highly advantageous to use a thermal printer to print information on a card, such as an ID card. When printing on an ID card, such cards are arranged in a card stack and placed in a hopper. They are serially fed by a feeding mechanism from the hopper into a feed path to a rotatable drum where they are secured to the drum and are printed. In order to operate the printer with a minimized cycle time and collect the cards in a stack, an effective high speed card ejecting apparatus has to be provided. Because of the stiffness of cards, misfeeding of cards is a problem in ejecting them from a thermal printer.